Stereospecific distribution of fatty acids in bovine milk fat triglycerides

Abstract

SUMMARYPancreatic lipase deacylation was used to study the variation in distribution of the fatty acids at positionsn-2 of milk fat triglycerides of a series of butters and of the milk obtained from a cow on a restricted feeding regimen. Selected samples were analysed for stereospecific distribution of their triglyceride fatty acids which were found to be esterified in a non-random manner. The percentage of a fatty acid at positionsn-3 generally decreased with increase in the chain length of the acid; the reverse occurred at positionsn-1. There was no major variation in the stereospecific distribution of fatty acids throughout the year; the variation that did occur was exhibited mainly by the medium chain length acids. Variation was greater at positionssn-1 andsn-3 than at positionsn-2 and when the proportion of an acid varied at positionsn-1 it usually varied at positionsn-3 in the reverse manner.For the milk samples it was found that change in triglyceride fatty acid composition was not associated with random increases or decreases of fatty acids at the 3 stereospecific positions. With changing triglyceride fatty acid composition (6:0, 8:0, 10:0, 12:0, 14:0, and 16:0 decreasing and 18:1 increasing) the percentage of 6:0, 8:0, 10:0, 12:0, 14:0 and 16:0 acids at positionsn-3 decreased while the percentage of 18:0 and 18:1 acids increased. These changes were compensated for by changes in the opposite direction at positionssn-1 andsn-2.